Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 163
Filtrar
Mais filtros

Base de dados
Tipo de documento
Intervalo de ano de publicação
1.
Nature ; 627(8004): 604-611, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38448582

RESUMO

Human brains vary across people and over time; such variation is not yet understood in cellular terms. Here we describe a relationship between people's cortical neurons and cortical astrocytes. We used single-nucleus RNA sequencing to analyse the prefrontal cortex of 191 human donors aged 22-97 years, including healthy individuals and people with schizophrenia. Latent-factor analysis of these data revealed that, in people whose cortical neurons more strongly expressed genes encoding synaptic components, cortical astrocytes more strongly expressed distinct genes with synaptic functions and genes for synthesizing cholesterol, an astrocyte-supplied component of synaptic membranes. We call this relationship the synaptic neuron and astrocyte program (SNAP). In schizophrenia and ageing-two conditions that involve declines in cognitive flexibility and plasticity1,2-cells divested from SNAP: astrocytes, glutamatergic (excitatory) neurons and GABAergic (inhibitory) neurons all showed reduced SNAP expression to corresponding degrees. The distinct astrocytic and neuronal components of SNAP both involved genes in which genetic risk factors for schizophrenia were strongly concentrated. SNAP, which varies quantitatively even among healthy people of similar age, may underlie many aspects of normal human interindividual differences and may be an important point of convergence for multiple kinds of pathophysiology.


Assuntos
Envelhecimento , Astrócitos , Neurônios , Córtex Pré-Frontal , Esquizofrenia , Adulto , Idoso , Idoso de 80 Anos ou mais , Humanos , Pessoa de Meia-Idade , Adulto Jovem , Envelhecimento/metabolismo , Envelhecimento/patologia , Astrócitos/citologia , Astrócitos/metabolismo , Astrócitos/patologia , Colesterol/metabolismo , Cognição , Neurônios GABAérgicos/metabolismo , Predisposição Genética para Doença , Glutamina/metabolismo , Saúde , Individualidade , Inibição Neural , Plasticidade Neuronal , Neurônios/citologia , Neurônios/metabolismo , Neurônios/patologia , Córtex Pré-Frontal/citologia , Córtex Pré-Frontal/metabolismo , Córtex Pré-Frontal/patologia , Esquizofrenia/genética , Esquizofrenia/metabolismo , Esquizofrenia/patologia , Análise da Expressão Gênica de Célula Única , Sinapses/genética , Sinapses/metabolismo , Sinapses/patologia , Membranas Sinápticas/química , Membranas Sinápticas/metabolismo
2.
Chemistry ; 29(63): e202302188, 2023 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-37566451

RESUMO

This work reports the effect of Pd(II) as chemical effector on an acylhydrazone-based dynamic covalent library (DCL) in biphasic systems (water/chloroform). The constituents of the DCL are self-built and distributed in the two phases, two of them are lipophilic enough to play the role of a carrier agent that may transfer Pd(II) from the aqueous phase to the organic phase. Upon addition of Pd(II), the DCL of components exhibits a strong amplification of the constituent that is the most adapted to stabilize Pd(II) in chloroform as well as its agonist in water. This evolution is driven by the combination of the interaction of the DCL with Pd(II) and the presence of the two phases. This study paves the way to a novel approach for liquid/liquid extraction and metal recovery by means of adaptive extractant species generated in situ by a DCL.

3.
Demography ; 60(6): 1711-1720, 2023 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-37982579

RESUMO

In this research note, we demonstrate that trends in the likelihood of child support agreements differ by marital history (i.e., never-married vs. ever-married) and by whether measures rely on the stock of families (i.e., all those in which children live apart from a parent) or the flow (i.e., those that include children who newly live apart from a parent) in a given year. While previous research has highlighted difference by marital history, the contrast between stock and flow is a new contribution. Trends are typically measured with reference to the stock of cases, even while the flow of cases, which more immediately reflects concurrent policy changes, is more relevant in many contexts. Interpretations of recent declines in child support agreements in the stock of cases-referenced as evidence for both mandating participation and the impracticality of requiring child support-may be better informed by considering the flow of cases. We find the flow of previously married mothers increasingly likely to have child support agreements while the likelihood is relatively consistent over time for never-married mothers. For both groups, using the flow measure, we find notable increases in agreements without payments due in the most recent period. These findings underscore the importance of differentiating stock and flow, and by marital history, in considering the proportion with agreements as an indicator of the effectiveness of current policy.


Assuntos
Custódia da Criança , Características da Família , Feminino , Criança , Humanos , Pais , Casamento , Mães
4.
J Sep Sci ; 46(20): e2300204, 2023 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-37568243

RESUMO

In striving for the best possible separation, the selectivity of stationary phases as an optimization parameter is often underestimated although there are many ways to influence this powerful tool. This review serves to provide an insight into the various ways of adapting the selectivity of a separation in liquid chromatography. Approaches via temperature and flow rate tuning are discussed as a basis followed by focusing on the stationary phase as the superior optimization parameter. Highly selective stationary phases hereby provide an advantage for groups of similar analytes. For more complex mixtures, separations can be improved using mixed-mode technologies where different retention mechanisms are combined. Serial coupling, mixed-bed columns, and stationary phase optimized selectivity liquid chromatography provide solutions to various degrees. Finally, the advantages of stationary phase tuning over adaption of mobile phase and/or temperature are presented in terms of optimum application range.

5.
Fam Process ; 62(3): 1196-1216, 2023 09.
Artigo em Inglês | MEDLINE | ID: mdl-36216325

RESUMO

Families (and sometimes courts) make important decisions regarding child physical custody arrangements post-separation, and shared parenting arrangements are increasingly common in most developed countries. Shared arrangements may be differentially associated with parental satisfaction, and these associations may vary across countries. Using data from surveys of separated mothers in Wisconsin and Finland, the present study explores this possibility and is guided by three aims: (a) to identify child and family characteristics associated with sole and shared child placements 6 or more years after separation; (b) to estimate associations of children's post-separation placements with maternal satisfaction with placements and expense sharing; (c) to examine whether the relationship between post-separation placement and maternal satisfaction varies by mothers' earnings and the quality of parents' relationships. We find that Finnish mothers with shared placement are more satisfied with their placement than are their counterparts with sole placement, while we find the inverse is true for Wisconsin mothers. Moreover, parental satisfaction with shared placement, overall and relative to sole placement, varies greatly depending on the quality of a mother's relationship with the other parent; and differences in relationship quality in Wisconsin and Finland may help explain the difference in satisfaction with shared placement in the two locations. In both Finland and Wisconsin, we find mothers with shared placement are more satisfied with the way expenses are shared between parents than are mothers with sole placement. Associations between placement and satisfaction are robust to extensive controls for child and maternal characteristics.


Assuntos
Custódia da Criança , Divórcio , Feminino , Humanos , Criança , Finlândia , Wisconsin , Mães , Satisfação Pessoal
6.
Soc Sci Res ; 110: 102850, 2023 02.
Artigo em Inglês | MEDLINE | ID: mdl-36796990

RESUMO

Research on child support compliance has focused on the characteristics of noncustodial parents (NCPs) that are associated with compliance, finding that compliance with child support orders is primarily related to the ability to pay support as demonstrated by earnings. Yet, there is evidence linking social support networks to both earnings and noncustodial parents' relationships with children. Using a social poverty framework, we show that relatively few NCPs are completely isolated: most have at least some people in their network who can loan money, provide a place to stay, or provide a ride. We explore whether the size of these instrumental support networks is positively linked to child support compliance both directly and indirectly through earnings. We find evidence of a direct association between instrumental support network size and child support compliance, but no evidence of an indirect association via increased earnings. These findings suggest the importance for researchers and child support practitioners to consider the contextual and relational factors of the social networks in which parents are embedded, and to more thoroughly examine the process by which support from one's network can lead to child support compliance.


Assuntos
Custódia da Criança , Pais , Criança , Humanos , Renda , Pobreza , Apoio Social
7.
J Cell Sci ; 133(5)2020 03 10.
Artigo em Inglês | MEDLINE | ID: mdl-32156720

RESUMO

Neutrophil extracellular traps (NETs) are one of the most intriguing discoveries in immunological research of the past few years. After their first description in 2004, the number of research articles on how NETs affect immunodefense, and also how they contribute to an ever-growing number of diseases, has skyrocketed. However, tempting as it may seem to plunge into pharmaceutical approaches to tamper with NET formation, our understanding of this complex process is still incomplete. Important concepts such as the context-dependent dual functions of NETs, in that they are both inflammatory and anti-inflammatory, or the major intra- and extracellular forces driving NET formation, are only emerging. In this Review, we summarize key aspects of our current understanding of NET formation (also termed NETosis), emphasize biophysical aspects and focus on three key principles - rearrangement and destabilization of the plasma membrane and the cytoskeleton, alterations and disassembly of the nuclear envelope, and chromatin decondensation as a driving force of intracellular reorganization.


Assuntos
Armadilhas Extracelulares , Membrana Celular , Cromatina , Neutrófilos , Membrana Nuclear
8.
Molecules ; 26(20)2021 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-34684817

RESUMO

A more sustainable management of natural resources and the establishment of processes allowing a joint management of nuclear materials to avoid their diversion from their civilian use are two issues for the nuclear industry. Short alternatives to existing processes have therefore been proposed based on known systems available, tributylphosphate (TBP), for the separation of actinides by liquid/liquid extraction. Proof of concept of such alternative has been established on the uranium(VI)/thorium(IV) system. From an organic phase consisting of a mixture of TBP/n-dodecane loaded with uranium and thorium, two fluxes have been obtained: the first contains almost all of the thorium in the presence of uranium in a controlled ratio, the second contains surplus uranium. Two levers were selected to control the spontaneous separation of the organic phase: the addition of concentrated nitric acid, or the temperature variation. Best results have been obtained using a temperature drop in the liquid/liquid extraction process, and variations in process conditions have been studied. Final metal recovery and solvent recycling have also been demonstrated, opening the door for further process development.

9.
Inorg Chem ; 59(5): 3260-3273, 2020 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-32043870

RESUMO

Within the development of future nuclear reactors, wet chemistry routes have been investigated for the fabrication of advanced oxide fuels. In this frame, a multiparametric study focused on the hydrothermal conversion of uranium(IV) oxalate U(C2O4)2·nH2O into uranium oxides was undertaken in order to unravel the effects of temperature, pH, and kinetics. For pH ≤ 1, the lowest temperatures explored (typically from 180 to 200 °C) led to stabilized UO2+x/U4O9 mixtures exhibiting a global O/U ratio evaluated as 2.38 ± 0.10 from U M4-edge HERFD-XANES experiments. Higher temperatures (220-250 °C) led the oxide stoichiometry to decrease down to 2.13 ± 0.04 which corresponds to a lower fraction of U4O9 in the mixture. Additionally, increasing the temperature of the hydrothermal treatment efficiently improved the elimination of residual carbon species and water. Hydrothermal conversion of U(C2O4)2·nH2O also led to a drastic modification of the powders morphology. With this aim, pH tuning could be used to shift from bipyramidal aggregates (up to pH 1) to microspheres (2 ≤ pH ≤ 5) and then to nanometric powders (pH > 5). Finally, a kinetics study showed that uranium oxides can be obtained from the hydrothermal decomposition of oxalate within only few hours. If the samples collected early during the treatment always presented the characteristic XRD lines of UO2+x/U4O9 fluorite-type structure, then they were found to be strongly oxidized (O/U = 2.65 ± 0.14) which suggested the existence of a U(VI)-bearing amorphous secondary phase. The latter further tended to reduce through time. Hydrothermal conversion then probably proceeds as a two-step mechanism composed by the oxidative decomposition of uranium(IV) oxalate followed by the reduction of uranium by organic moieties and its hydrolysis. It appears as an easy and efficient way to yield highly pure uranium oxide samples in solution.

10.
Environ Sci Technol ; 54(15): 9681-9692, 2020 08 04.
Artigo em Inglês | MEDLINE | ID: mdl-32644805

RESUMO

The development of environmentally benign hydrometallurgical processes to treat spent lithium-ion batteries (LIBs) is a critical aspect of the electronic-waste circular economy. Herein, as an alternative to the highly explosive H2O2, discarded orange peel powder (OP) is valorized as a green reductant for the leaching of industrially produced LIBs scraps in citric acid (H3Cit) lixiviant. The reductive potential of the cellulose- and antioxidant-rich OP was validated using the 3,5-dinitrosalicylic acid and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic) acid assays. Leaching parameters such as OP concentration (200 mg), processing temperature (100 °C), H3Cit concentration (1.5 M), reaction duration (4 h), and slurry density (25 g/mL) were systematically optimized to achieve 80-99% leaching efficiencies of Ni, Mn, Co, and Li from the LIB "black mass". Importantly, solid side-streams generated by the OP-enabled leaching displayed negligible cytotoxicity in three different human cell lines, suggesting that the process is environmentally safe. As a proof of concept, Co(OH)2 was selectively recovered from the green lixiviant and subsequently utilized to fabricate new batches of LiCoO2 (LCO) coin cell batteries. Galvanostatic charge-discharge test revealed that the regenerated batteries exhibited initial charge and discharge values of 120 and 103 mAh/g, respectively, which is comparable to the performance of commercial LCO batteries. The use of fruit peel waste to recover valuable metals from spent LIBs is an effective, ecofriendly, and sustainable strategy to minimize the environmental footprint of both waste types.


Assuntos
Lítio , Substâncias Redutoras , Fontes de Energia Elétrica , Frutas , Peróxido de Hidrogênio , Reciclagem
11.
Nano Lett ; 19(9): 6604-6611, 2019 09 11.
Artigo em Inglês | MEDLINE | ID: mdl-31418577

RESUMO

Serotonin is an important neurotransmitter involved in various functions of the nervous, blood, and immune system. In general, detection of small biomolecules such as serotonin in real time with high spatial and temporal resolution remains challenging with conventional sensors and methods. In this work, we designed a near-infrared (nIR) fluorescent nanosensor (NIRSer) based on fluorescent single-walled carbon nanotubes (SWCNTs) to image the release of serotonin from human blood platelets in real time. The nanosensor consists of a nonbleaching SWCNT backbone, which is fluorescent in the beneficial nIR tissue transparency window (800-1700 nm) and a serotonin binding DNA aptamer. The fluorescence of the NIRSer sensor (995 nm emission wavelength for (6,5)-SWCNTs) increases in response to serotonin by a factor up to 1.8. It detects serotonin reversibly with a dissociation constant of 301 nM ± 138 nM and a dynamic linear range in the physiologically relevant region from 100 nM to 1 µM. As a proof of principle, we detected serotonin release patterns from activated platelets on the single-cell level. Imaging of the nanosensors around and under the platelets enabled us to locate hot spots of serotonin release and quantify the time delay (≈ 21-30 s) between stimulation and release in a population of platelets, highlighting the spatiotemporal resolution of this nanosensor approach. In summary, we report a nIR fluorescent nanosensor for the neurotransmitter serotonin and show its potential for imaging of chemical communication between cells.


Assuntos
Técnicas Biossensoriais , Plaquetas/metabolismo , Corantes Fluorescentes/química , Nanotubos de Carbono/química , Serotonina/metabolismo , Plaquetas/ultraestrutura , Humanos
12.
Chemistry ; 25(50): 11646-11649, 2019 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-31359455

RESUMO

A very concise total synthesis of (+)-brefeldin C starting from 2-furanylcyclopentene is described. This approach is based on an unprecedented enantioselective radical hydroalkynylation process to introduce the two cyclopentane stereocenters in a single step. The use of a furan substituent allows a high trans diastereoselectivity to be achieved during the radical process and it contains the four carbon atoms C1-C4 of the natural product in an oxidation state closely related to the one of the target molecule. The eight-step synthesis requires six product purifications and it provides (+)-brefeldin C in 18 % overall yield.

13.
Proc Natl Acad Sci U S A ; 113(29): 8093-7, 2016 07 19.
Artigo em Inglês | MEDLINE | ID: mdl-27370799

RESUMO

Applying the high-energy resolution fluorescence-detection (HERFD) mode of X-ray absorption spectroscopy (XAS), we were able to probe, for the first time to our knowledge, the crystalline electric field (CEF) splittings of the [Formula: see text] shell directly in the HERFD-XAS spectra of actinides. Using ThO2 as an example, data measured at the Th 3d edge were interpreted within the framework of the Anderson impurity model. Because the charge-transfer satellites were also resolved in the HERFD-XAS spectra, the analysis of these satellites revealed that ThO2 is not an ionic compound as previously believed. The Th [Formula: see text] occupancy in the ground state was estimated to be twice that of the Th [Formula: see text] states. We demonstrate that HERFD-XAS allows for characterization of the CEF interaction and degree of covalency in the ground state of actinide compounds as it is extensively done for 3d transition metal systems.

14.
Chemistry ; 24(47): 12241-12245, 2018 Aug 22.
Artigo em Inglês | MEDLINE | ID: mdl-29488660

RESUMO

Specific functionalization of 1D nanomaterials such as near infrared (nIR) fluorescent single-walled carbon nanotubes (SWCNTs) is essential for colloidal stability and tailoring of their interactions with the environment. Here, we show that de novo designed alpha-helical coiled-coil peptide barrels (αHBs) with appropriate pores encapsulate and solubilize SWCNTs. In contrast, barrels without or with narrow pores showed a much smaller efficiency. Absorption/fluorescence spectroscopy and atomic force microscopy indicate that the SWCNTs are incorporated into the αHB's pore. The resulting hybrid SWCNT@αHBs display periodic surface coverage with a 40 nm pitch and remain fluorescent in the nIR. This approach presents a novel concept to encapsulate, discriminate and functionalize SWCNTs non-covalently with peptides and holds great promise for future applications in bioimaging or drug delivery.


Assuntos
Nanotubos de Carbono/química , Peptídeos/química , Sequência de Aminoácidos , Técnicas Biossensoriais , Microscopia de Força Atômica , Microscopia de Fluorescência , Estrutura Secundária de Proteína
15.
An Acad Bras Cienc ; 90(3): 2741-2752, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30304219

RESUMO

Accidents caused by leaks and/or spills on soils need to be addressed. Natural attenuation, biostimulation and bioaugmentation can be useful bioremediation strategies for decontamination processes in soils of diesel/biodiesel mixtures. The purpose of this study was to evaluate the degradation rate of the different fuels (B0, B20 and B100) in an ultisol under natural attenuation and biostimulation/bioaugmentation during 60 days of incubation in a controlled microcosm simulating a surface spill over soil. The degradation of different diesel/biodiesel mixtures was monitored for up to 60 days by dehydrogenase activity, respirometry by CO2 release, the most probable number of heterotrophic and degrading microorganism and gas chromatography. The bacterial inoculum employed for biostimulation/bioaugmentation strategy consisted of Bacillus megaterium, Bacillus pumilus, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia. The two bioremediation strategies have showed great degradation rates. The natural attenuation was effective for B0 and B20 treatments. The addition of the bacterial consortium and macronutrients contributed to the increased degradation of pure biodiesel in relation to natural attenuation, with higher rates for CO2 release, enzymatic and degrading activity. It is suggested that the bacterial consortium has proven effective for presenting significant values for such parameters until the end of the 60-day incubation period.


Assuntos
Biodegradação Ambiental , Biocombustíveis , Poluição Ambiental , Gasolina , Poluentes do Solo/metabolismo , Bacillus megaterium/metabolismo , Bacillus pumilus/metabolismo , Pseudomonas aeruginosa/metabolismo , Stenotrophomonas maltophilia/metabolismo
16.
J Environ Manage ; 214: 17-22, 2018 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-29518592

RESUMO

The Zr based metal organic framework, UiO-66, has been synthesized along with its isostructural equivalence tetrafluorinated, the UiO-66-F4. The corresponding ligands to these MOFs are the widely used BDC (1,4-benzenedicarboxylic acid) and the TFBDC (2,3,5,6-Tetrafluoro-1,4-benzenedicarboxylic acid). These coordination materials have been tested towards the sorption of the organic pollutants (Benzene, Toluene, Ethylbenzene and Xylene) in aqueous phase and both materials showed capacities to adsorb all the pollutants. It has been possible to compare the efficiency in the adsorption of two iso-structural MOFs, which will behave differently due to the hydrophobic behavior of the UiO-66-F4 MOF. The addition of F in the structure of the ligand of the MOF allows to obtain a hydrophobic material by changing the nature of the interactions between the adsorbent and the adsorbate from π-π stacking in the pristine UiO-66 to hydrophobic interactions in the UiO-66-F4. However, size of the pores has also revealed an important effect, since steric impediments will decrease the capacity of the fluorinated MOF towards the sorption of bigger molecules.


Assuntos
Poluentes Ambientais/química , Estruturas Metalorgânicas , Adsorção , Benzeno , Tolueno , Xilenos
17.
Chemphyschem ; 18(24): 3583-3594, 2017 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-29024271

RESUMO

With the need for a precise description of the long-range electronic effects of a perfloroalkyl chain (F-ponytail) grafted onto metal chelators, we studied in detail the effect of a spacer inserted between the polar complexing head and the F-ponytail, in relation to the metal coordination ability of the resulting molecules. The prepared molecules were then applied for the extraction of various metals from an aqueous phase into an organic phase, and the optimum spacer length could be estimated to be between three and four methylene units, according to the extraction conditions. The study also revealed the difficulty of modeling and anticipating the tiny energy differences involved in the extraction process and the importance in peculiar cases to go beyond only these studied inductive effects to understand better the factors that govern the stabilization of a metallic cation in a complex fluorous phase.

18.
Bioorg Med Chem ; 25(22): 6098-6101, 2017 11 15.
Artigo em Inglês | MEDLINE | ID: mdl-28341405

RESUMO

Several artemisinin derivatives carrying several groups (alkyl, hydroxyalkyl, allyl or azide) at position 9 have been synthesized starting from artemisinin via enolate formation and subsequent reaction with appropriate electrophiles.


Assuntos
Artemisininas/síntese química , Carbono/química , Aldeídos/química , Antimaláricos/síntese química , Antimaláricos/química , Antimaláricos/farmacologia , Artemisininas/química , Artemisininas/farmacologia , Plasmodium falciparum/efeitos dos fármacos , Estereoisomerismo
19.
Sensors (Basel) ; 17(7)2017 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-28657584

RESUMO

Detection of neurotransmitters is an analytical challenge and essential to understand neuronal networks in the brain and associated diseases. However, most methods do not provide sufficient spatial, temporal, or chemical resolution. Near-infrared (NIR) fluorescent single-walled carbon nanotubes (SWCNTs) have been used as building blocks for sensors/probes that detect catecholamine neurotransmitters, including dopamine. This approach provides a high spatial and temporal resolution, but it is not understood if these sensors are able to distinguish dopamine from similar catecholamine neurotransmitters, such as epinephrine or norepinephrine. In this work, the organic phase (DNA sequence) around SWCNTs was varied to create sensors with different selectivity and sensitivity for catecholamine neurotransmitters. Most DNA-functionalized SWCNTs responded to catecholamine neurotransmitters, but both dissociation constants (Kd) and limits of detection were highly dependent on functionalization (sequence). Kd values span a range of 2.3 nM (SWCNT-(GC)15 + norepinephrine) to 9.4 µM (SWCNT-(AT)15 + dopamine) and limits of detection are mostly in the single-digit nM regime. Additionally, sensors of different SWCNT chirality show different fluorescence increases. Moreover, certain sensors (e.g., SWCNT-(GT)10) distinguish between different catecholamines, such as dopamine and norepinephrine at low concentrations (50 nM). These results show that SWCNTs functionalized with certain DNA sequences are able to discriminate between catecholamine neurotransmitters or to detect them in the presence of interfering substances of similar structure. Such sensors will be useful to measure and study neurotransmitter signaling in complex biological settings.

20.
Angew Chem Int Ed Engl ; 56(36): 10858-10861, 2017 08 28.
Artigo em Inglês | MEDLINE | ID: mdl-28598018

RESUMO

A one-pot procedure for the enantioselective hydroazidation of non-activated trisubstituted alkenes is described. Hydroboration with monoisopinocampheylborane (IpcBH2 ) provides dialkylboranes that are in situ selectively converted into monoalkyl-substituted catecholboranes; these undergo radical azidation upon treatment with benzenesulfonyl azide and a radical initiator. Enantiomerically enriched azides were thus obtained in yields of 59-81 % and enantioselectivities of up to 94:6 e.r. (98:2 e.r. if the intermediate dialkylborane is purified by crystallization). A rapid access to enantiomerically pure (+)-rodocaine is also described. The use of other arenesulfonyl radical traps enables enantioselective hydroallylation, hydrosulfanylation, and hydrobromination reactions with yields of 71-86 %.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA